Third year of an ongoing program dealing with sociosexual behavior in dogs. Major emphasis this year is on physiological and behavioral changes associated with puberty and sexual maturation in the male. Normal puppies are observed periodically through the first year of life starting at birth. A second group of males is treated with testosterone in an attempt to induce precocious puberty, and a third group is castrated in infancy to delay or prevent sexual maturation. Types of behavior studied include the following: Development of juvenile and then adult masculine urination postures. Appearance of male mating responses. Social dominance over females. Responsiveness to "sexual" stimuli such as odor of estrous female, etc. BBILIOGRAPHIC REFERENCES: Beach, F.A., and M.G. Buehler. 1977. Male rats with inherited insensitivity to androgen show reduced sexual behavior. Endocrin. 100, 197-200. Beach F.A. Editor. Human Sexuality in Four Perspectives, John Hopkins Press, 1977.